1. Field of the Invention
This invention relates to the field of melting furnaces for metal production. More particularly it pertains to a roof or lid assembly for such furnaces formed of refractory material and in relatively large segments assembled during construction.
2. Description of the Prior Art
It is conventional practice to fabricate the roof of round, top-charged melting furnaces using many interlocking refractory bricks. For a typical furnace having a diameter of 26 feet, approximately 6500 bricks in four shapes are required. As the roof is formed, the diameter of each row of bricks is reduced, therefore requiring a different brick shape to produce a near perfect fit. Each brick is individually mortared and placed by hand; a long, labor intensive process. However, because of the large number of brick shapes required to produce a perfect fit, a lesser number is used to produce a reasonably acceptable, less perfect fit. Furthermore, the various brick shapes are difficult and costly to produce.
Top overcome these and other problems, various techniques employing larger building units than bricks have been devised. For example, U.S. Pat. No. 4,021,603 describes a domed furnace roof assembled from panels of cast iron having an embedded cooling coil for carrying cooling water. A central panel closes the roof surface, which is bounded by a circumferential ring. U.S. Pat. No. 4,453,253 describes use of wedge-shaped refractory roof blocks arranged to extend between a furnace wall and a polygonal center panel to form a domed roof.
The U.S. patent to Kramer (U.S. Pat. No. 3,621,627) describes a refractory grid of panels whose radially directed, adjacent edges are alternately beveled inwardly downward and outwardly downward, thereby interlocking the panels.
U.S. Pat. No. 3,434,263 shows a technique for forming a grout key in recesses at the faces of precast concrete blocks. The keys form a shear connection between the blocks. The U.S. patent to Watry (U.S. Pat. No. 4,147,009) shows a recessed keyway filled with mortar to join precast panels. U.S. Pat. No. 2,465,822 describes a furnace lid of wedge-shaped refractory elements, whose adjacent faces are held in place by a peripheral band.